Study of heavy-lepton production ine+e−annihilation

We present a numerical study of the collinearity-angle distribution for $e$ and $\mu$ in the process $e\overline{e}\to L\overline{L}$ and the subsequent decay $L\to {\nu }_L+l+{\overline{\nu }}_l$, $l=\mu or e$. $V+A$ as well as $V-A$ couplings for the heavy lepton are considered together with a nonvanishing mass for ${\nu }_L$. A $V+A$ current with a massless or massive neutrino or a $V-A$ current with a massive neutrino gives rise to more $e\mu$ events at smaller collinearity angles than the standard $V-A$ sequential lepton with a massless neutrino. A smaller heavy-lepton mass and larger experimental energy cutoff also give rise to smaller collinearity angles. It appears to be possible to distinguish these dynamical and kinematical effects based on experimental data with better statistics than available at present. We note that the experimental determination of the leptonic branching ratio is sensitive to the coupling scheme and the neutrino mass. We present an expected collinearity-angle distribution for $l\pi$ events ($l=\mu or e$), which may be conveniently used to fix the mass of ${\nu }_L$. The effects of the possible existence of heavy leptons on the decreasing charged energy fraction in $e\overline{e}$ annihilation are also briefly discussed on the basis of recent data. A heavy lepton with mass ∼ 1.8 GeV can account for the decrease up to $W\sim 6$ GeV. To explain the further decrease in the charged energy fraction entirely in terms of heavy leptons, however, another heavy lepton with mass ∼ 2.8 GeV accompanied by a massive neutrino is required. We comment on the effects of such heavier leptons on the $e\mu$ cross section.